We have obtained preliminary evidence that the extracellular matrix component fibronectin is involved in two morphogenetic processes: Somite formation in the chick embryo; and a cyclical change in tissue morphology in the neural gland of the marine ascidian Ciona intestinalis. During somitogenesis, there is evidence of an increased adhesivity of segmental plate cells. During a tidal-associated biological rhythm, the cells of the neural gland in Ciona intestinalis aggregate and disaggregate every 6.2 hrs, and the aggregation is associated with an increase in the binding of anti-fibronectin (mammalian) by the gland cells. So far, experimental work has only been performed on somites, where the addition of exogenous cell-associated (soluble) mammalian fibronectin to dissociated embryonic chick segmental plate cells enhances their aggregation with 4 hrs. Plasma fibronectin does not have this effect. Similarly supplied cell-associated fibronectin to whole embryos speeds up the rate of somite formation, whereas plasma fibronectin has no effect. The proposed research seeks to extend these preliminary findings. 1) We wish to see if the difference in the effects of fibronectin (cell-associated vs. plasma) is biologically meaninful, and not due to differing sources or methods of preparation. We will prepare embryonic chick FN (both types) to determine their effect upon segmental plate cell aggregation and upon somitogenesis. 2) We will prepare antiserum to our chick fibronectins to use both for histo-immunological studies and to see if anti-fibronectin will interfere with the two processes under study (cell aggregation and somitogenesis). 3) Does FN act as an adhesion molecule in the ascidian neural gland? Gland cells have been isolated in both their aggregated and disaggregated state and observed under Nomarski optics in a feasbility study. Presently available fibronectin (obtained from colleagues or commercially) will be added to these cell sto see if aggregation can be promoted. 4) Histo-immunlogical studies can lead to interpretive errors, and should be confirmed with biochemical analyses when possible. In both studies we will isolate and characterize fibronectin. This may lead to difficulties in the case of the ascidians, since there are no published methods for characterizing invertebrate fibronectins. If we are successful in obtaining a 'FN' preparation from the ascidians, then we can test this preparation for its effect on aggregation.